The components to be mounted in the motor vehicles driven in roads, such as motorcycles and automobiles, have to comply with strict regulations which guarantee their maximum safety and reliability.
Hydraulic brake lines, among others, are components whose performance in the vehicle has a direct impact on its safety and reliability. Hydraulic brake lines, also known as brake lines, consist of a hydraulic circuit capable of pressurized fluid transmission between the different components forming a brake system, such as for example between the master cylinder and the ABS system, between the ABS set and the brake caliper or directly between the master cylinder and the brake caliper. The hydraulic brake lines usually comprise brake pipes, brake hoses and union terminals to the aforementioned equipment or other equipment. The combination of brake pipes and brake hoses allows reducing the efforts of the hydraulic brake lines itself and the vibrations transmitted to the different components of the vehicle, as well as allowing the movement of certain components of the vehicle. Precisely, one of the inconveniences of the hydraulic brake lines is found in the connections between brake pipes and brake hoses.
The present invention refers to a brake pipe connection to a brake hose, for the configuration of a hydraulic brake line, pursuant to DIN 74234, SAE J1401 and FMVSS 106 regulations. Particularly, the connection is especially suitable for brake hoses of an internal diameter of approximately 3.175 mm (⅛″) connected to brake pipes with a larger external diameter than the said internal diameter. One of the most widely used pipes in hydraulic brake lines is the one known as bundy tube. This bundy tube is made mainly of steel coated in a copper layer. Additionally, it can also be zinc coated with an additional polymeric coating to improve its corrosion resistance. The bundy tube is highly rigid and, therefore, it has less expansion volume when hydraulic fluids circulate through it at a very high pressure.
The difficulty posed by the brake pipe connection to a brake hose focuses mainly on the strict compliance with the choking or constriction requirements of the aforementioned regulations. Specifically, said regulations require that once assembled both tubes need to have a section for the passage of hydraulic fluid with a nominal internal diameter higher than 64% of the nominal internal diameter of the brake pipe, along the entire course of the hydraulic circuit.
Nowadays, the connection of a brake pipe to a brake hose of an internal diameter of approximately 3.175 mm (⅛″), pursuant to DIN 74234, SAE J1401 and FMVSS 106 regulations, can be performed in the following ways.
The first of them requires the use of an independent connection pipette. Said pipette has an external diameter which coincides, considering certain allowances, with the internal diameter of the brake hose. The connection also requires the use of a fixing bushing capable of housing the connection pipette inside it and receiving both the brake pipe and the brake hose through its ends. The assembly process begins with the insertion of the brake pipe in the bushing enabled to that end. Next, the bushing end is pressed to keep it together with the pipe, so that any of the components may move during the welding stage. The welding is carried out by capillarity inside a furnace and it requires a previous supply of copper between the brake pipe and the bushing end. The welding serves to guarantee the tightness of the connection between the brake pipe and the bushing and to make sure that the union is not destroyed when the assembly is subjected to certain traction forces. After the welding is performed, there is an electrolytic coating stage needed to avoid corrosion. The pipette is later inserted on the inside of the bushing, thus communicating the inlet hole in the brake pipe for the hydraulic fluid with the inlet hole in the pipette. After that, the brake hose is inserted in the other end of the bushing until the pipette is inserted under pressure on the inside of the brake hose, thus communicating the inlet hole in the pipette with the inlet hole in the brake hose. Finally, the rest of the bushing is pressed to increase the brake hose fixing and guaranteeing the tightness of the connection. This connection mode is normally used in steel braided hoses.
In the second connection mode known the pipette is not independent but it is integrated in fixing bushing itself. In spite of this noticeable difference, the assembly process coincides with the previously described one, the only difference being that it is not necessary to insert the pipette in the bushing as it is integrated therein. This connection mode is normally used in rubber hoses.
The main problems of the aforementioned processes are found in the welding and electrolytic coating stages.
As regards the inconveniences of the welding stage, once the brake pipe is inserted in the bushing end and said end is pressed so that both elements are kept together, it is put in the furnace to carry out the said welding stage. Since the bushing and the brake pipe are joined together, the welding stage makes it inevitable to put considerably large pieces in the furnace, according to the configuration required by the hydraulic brake line. Said pieces are hard and uncomfortable to manipulate and process, besides considerable increasing the welding time, and therefore the efficiency of the processes is reduced, as a smaller number of pieces can be fitted in the furnace than when the pieces have a smaller volume. Furthermore, bigger furnaces are also needed, which increases power consumption. Another inconvenience of the welding stage is that it does not allow using brake pipes with polymeric coating since putting them in the furnace would destroy said coating. The brake pipes with polymeric coatings, besides offering an excellent corrosion resistance, do not leave any residue when handled, and the end forming and brake pipe bending processes are therefore cleaner. Since the brake pipe with polymeric coating cannot be used, an electrolytic coating stage becomes necessary.
As regards the inconveniences of the electrolytic coating stage, it poses the same problems previously described regarding the welding stage, insofar as the uncomfortable handling of considerably large pieces through the electrolytic coating and efficiency reduction of the process. Besides, the corrosion resistance provided by the electrolytic coating is noticeably lower than the corrosion resistance offered by the polymeric coating, which also features a more reliable quality control through simple visual verification.
The present invention satisfactorily solves the aforementioned problems thanks to an assembly procedure, which is much more efficient and less expensive than the aforementioned processes, does not need the welding and electrolytic coating stages, enables to use brake pipes with polymeric coating and is based on a connection that integrates the connection pipette at the end of the brake pipe.